| As a new kind of wall energy-saving technology,phase change energy storage wall can not only improve the heat insulation performance of the wall,but also improve the heat storage performance of the wall and the comfort of building indoor environment.However,more research is needed on the practical engineering feasibility of the phase change energy storage wall,the heat transfer characteristics and the influence law of building energy consumption.By using numerical simulation,physical simulation experiment and theoretical analysis,the preparation method and basic properties of room-temperature composite phase change energy storage motor was studied,the determination method for appropriate phase change temperature of phase change walls was explored,the heat transfer characteristics and influence laws on building indoor temperature and consumption of different structural phase change walls were revealed.The main research conclusions and innovations are as follows:(1)Composite phase change mortar suitable for building room temperature environment was developed,and the preparation method integrating raw material,composition,adsorption,package and preparation for new kind phase change energy storage motor was obtained.Using solid and liquid paraffin as raw materials,composite phase change paraffin with a phase change temperature by means of heat co-melting was prepared which possessed high phase change enthalpy and thermal stability.Phase change ceramics in which composite phase change paraffin could be absorbed up to 58%were prepared by using epoxy resin as encapsulating material and ceramic as porous adsorption carrier.The phase change mortar was prepared by replacing medium sand with phase change ceramic grains,and the suitable replacing amount was 50%,the compressive strength and thermal conductivity of the phase change mortar with suitable mix ratio were 9.33MPa and 0.739w/(m·K),possessing good mechanical and thermal properties.(2)The method to determine the suitable phase transition temperature of phase change energy storage building wall considering building direction and structure was proposed,then suitable phase change temperature for phase change energy storage wall in summer working condition was obtained.Heat-transfer processes for different structural phase change walls were simulated by ANSYS using surface air temperature of different directional walls in summer in Xuzhou as boundary conditions.Outer surface average temperature at phase change layer was confirmed as suitable phase change temperature based on the interior surface temperature.Suitable phase change temperature declined from outer to inner with the phase change layer,highest the outer phase change wall and lowest the inner.Suitable phase transition temperature was affected obviously by the wall direction,highest in west.(3)Experimental testing method for heat transfer characteristics of phase change wall was proposed.Artificial environmental testing platform simulating summer outdoor environment was designed,and physical experiments for heat transfer characteristics of outer,sandwich and inner structural phase change wall were completed.Numerical simulation of heat transfer characteristics for three structural types of phase change wall were calculated using experimental testing temperatures as boundary conditions.Comparing experimental testing results to simulation calculating results,average error rate was less than 5%,and well verified each other coherently.(4)Heat transfer characteristics of phase change energy storage wall were revealed,and the influence of the temperature,enthalpy and thickness of the phase change layer on the heat transfer characteristics of the outer wall was received.Heat transfer processing mathematical model of phase change walls was established based on one dimensional unsteady heat transfer theory for phase changing process.Heat transfer characteristics of different structural phase change energy storage walls were revealed according to experiment testing and simulation calculating results of heat transfer process.Outer phase change wall's thermal insulation performance was best among three different structural walls,inner surface maximum temperature decreased 0.4?,average heat-transfer coefficient reduced 28.3%,attenuation multiple increased 65.8%,and delay time increased 2h.Thermal insulation properties for outer phase change walls could be affected significantly by the phase change temperature,enthalpy value and phase change layer thickness.(5)The changing laws of indoor temperature for test box with inner phase change wall under artificial environment condition and test room with outer phase change wall under natural environment condition were obtained.Air temperature in closed inner phase change test box was higher than in common test box under artificial alternating temperature which was against for building energy saving in summer.Increasing and decreasing rate of the air temperature in test box was less than in common test box under heating and cooling condition,which revealed that outer phase change wall was decreasing indoor air temperature and reducing indoor temperature fluctuation.(6)The influencing laws of phase change energy storage walls on building energy consumption were obtained,and optimum design methods of phase change energy storage walls in summer working condition were proposed.According to the principles of climate and building application and best performance,heat transfer characteristics and building energy consumption,optimum design parameters of phase change walls in summer working condition in Xuzhou were determined using numerical simulation calculation as tools.Outer phase change walls could be the suitable wall structure,and the suitable phase change temperatures for east,south,west and north direction were 31.3?,31.2?,32.1?and31.2?,and the Total enthalpy value for suitable phase change was 2400kJ/m~2.The building indoor thermal environment could be improved with optimum designed outer phase change walls,while the AC energy consumption declined. |
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